1. Field of the Invention
The invention relates generally to turbo pumps, and, more particularly, turbo pumps having an impeller magnetically supported in a casing from outside of the casing without being mechanically supported.
2. Description of the Background Art
A turbo pump is a pump for providing energy to fluid by way of the rotation of the impeller, and widely known in the industrial world.
FIGS. 1 and 2 are sectional views showing a conventional turbo pump used in biotechnology, semiconductor manufacturing technologies, and medical instruments, etc. Referring to FIG. 1, a pump 10 includes an impeller 11 for providing a rotary motion to the fluid. The impeller 11 is mechanically supported by a rotating shaft 12, with the rotating shaft 12 being supported by a rolling bearing 13 and driven by a motor 14. When the rotating shaft 12 is rotated by the motor 14, the impeller 11 mechanically supported at the rotating shaft 12 rotates. By the rotation of the impeller 11, the fluid is sucked from a suction tube 16, and then discharged through a scroll chamber 17.
A pump used in biotechnology, semiconductor manufacturing technologies, and medical instruments is required to be extremely clean. Accordingly, in the pump 10 shown in FIG. 1, in order to isolate the fluid from the rolling bearing 13 and the motor 14 generating contaminants which contaminate the fluid, a seal 15 is provided between the impeller 11 and the bearing 13. The seal 15 is, however, in contact with the rotating shaft 12, so that there are disadvantages that the fluid may be contaminated by the contaminants generated in this contacting portion, and that the fluid may change in quality by the frictional heat. In addition, it is impossible for the seal 15 to completely prevent the contaminants produced from the bearing 13 and the motor 14 from entering the fluid.
In order to eliminate these disadvantages, there is shown a pump 20 in FIG. 2, having a magnetic bearing instead of a rolling bearing, an electromagnet of a motor, etc. being sealed, and a portion made of iron or iron member being plated, so that no seal is required.
Referring to FIG. 2, a rotating shaft 22 for an impeller 21 is supported by a radial magnetic bearing 23 and an axial magnetic bearing 24, and rotated by a motor 25. While the fluid enters the spindle 26, it is not contaminated as the iron member or the coil of the motor 25 and the magnetic bearings 23, 24 is sealed or plated.
In the pump shown in FIG. 2, however, there is a place where the fluid stagnates in the spindle 26, so that it is not preferable to apply such a pump to biotechnology and medical instruments. For example, if it is applied to an artificial heart, there occur thrombi due to the stagnation of the blood, so that the life is endangered.